Method of forming an array of a multi-device unit cell

ABSTRACT

Backplane-side bonding structures including a common metal are formed on a backplane. Multiple source coupons are provided such that each source coupon includes a transfer substrate and an array of devices to be transferred. Each array of devices are arranged such that each array includes a unit cell structure including multiple devices of the same type and different types of bonding structures including different metals that provide different eutectic temperatures with the common metal. Different types of devices can be sequentially transferred to the backplane by sequentially applying the supply coupons and selecting devices providing progressively higher eutectic temperatures between respective bonding pads and the backplane-side bonding structures. Previously transferred devices stay on the backplane during subsequent transfer processes, enabling formation of arrays of different devices on the backplane.

FIELD

The embodiments of the invention are directed generally to an array of amulti-device unit cell such as an emissive display panel employing alight emitting device array on a backplane, and a method ofmanufacturing the same.

BACKGROUND

A device array including semiconductor devices such as light emittingdiodes can be employed for various applications. For example, an arrayof light emitting devices is used in electronic displays, such as directview display devices.

SUMMARY

According to an aspect of the present disclosure, a method of forming adevice assembly is provided. The method of forming a device assemblyincludes: a step of providing a backplane including a periodic array ofmultiple instances of a backplane-side unit cell structure thatcomprises a set of backplane-side bonding structures including a commonmetal; a step of providing a first source coupon including a firsttransfer substrate and a periodic array of multiple instances of a firstunit cell structure that comprises at least one first device and havinga same periodicity as the periodic array of multiple instances of thebackplane-side unit cell structure, wherein an instance of a firstdevice-side bonding structure including a first metal is provided on onefirst device per each first unit cell structure, and the common metaland the first metal are selected to provide a first bonding metallurgyhaving a first eutectic temperature upon bonding; a step of transferringone first device from each instance of the first unit cell structure tothe backplane by bonding respective instances of the first device-sidebonding structure to matching backplane-side bonding structures, whereina periodic array of first bonded material portions having the firstbonding metallurgy is formed while backplane-side bonding structuresthat are not bonded do not reflow; a step of providing a second sourcecoupon including a second transfer substrate and a periodic array ofmultiple instances of a second unit cell structure that comprises atleast one second device and having a same periodicity as the periodicarray of multiple instances of the backplane-side unit cell structure,wherein an instance of a second device-side bonding structure includinga second metal is provided on one second device per each second unitcell structure, and the common metal and the second metal are selectedto provide a second bonding metallurgy having a second eutectictemperature upon bonding, and the second eutectic temperature is greaterthan the first eutectic temperature; and a step of transferring onesecond device from each instance of the second unit cell structure tothe backplane by bonding respective instances of the second device-sidebonding structure to matching backplane-side bonding structures.

According to another aspect of the present disclosure, a device assemblycomprising a periodic array of multiple instances of a unit cellstructure is provided. Each instance of the unit cell structurecomprises: a first device bonded to the backplane through a first bondedmaterial portion employing a first bonding metallurgy; and a seconddevice bonded to the backplane through a second bonded material portionemploying a second bonding metallurgy. The first bonding metallurgy andthe second bonding metallurgy include a common metal. The first bondingmetallurgy includes a first metal that is not present in the secondbonding metallurgy. The second bonding metallurgy includes a secondmetal that is not present in the first bonding metallurgy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the step of generation ofassemblies of growth substrates with respective devices thereupon frominitial growth substrates according to an embodiment of the presentdisclosure.

FIG. 2 is a schematic illustration of the step of bonding of the growthsubstrates to respective first carrier substrates through the respectivedevices according to an embodiment of the present disclosure.

FIG. 3 is a schematic illustration of the step of removing the growthsubstrates according to an embodiment of the present disclosure.

FIG. 4 is a schematic illustration of the step of forming a firstbonding material layer on the first carrier substrates, providing secondcarrier substrate, and forming a release layer and a second bondingmaterial layer according to an embodiment of the present disclosure.

FIG. 5 is a schematic illustration of the step of bonding each pair of afirst carrier substrate and a second carrier substrate according to anembodiment of the present disclosure.

FIG. 6 is a schematic illustration of the step in which each firstcarrier substrate is removed from a bonded structure according to anembodiment of the present disclosure.

FIGS. 7A-7E are sequential schematic top-down views of supply couponsand backplanes during various steps of a transfer sequence according toan embodiment of the present disclosure.

FIGS. 8A-8C, 8E-8I, 8K-8O, 8Q-8U, 8W, and 8X are sequential verticalcross-sectional view of a first backplane and source coupons employed totransfer devices to multiple backplanes according to an embodiment ofthe present disclosure.

FIG. 8D is a vertical cross-sectional view of an alternative structurefor the structure of FIG. 8C according to an embodiment of the presentdisclosure.

FIG. 8J is a vertical cross-sectional view of an alternative structurefor the structure of FIG. 8I according to an embodiment of the presentdisclosure.

FIG. 8P is a vertical cross-sectional view of an alternative structurefor the structure of FIG. 8O according to an embodiment of the presentdisclosure.

FIG. 8V is a vertical cross-sectional view of an alternative structurefor the structure of FIG. 8U according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

As stated above, the present disclosure is directed to an assembly ofintegrated back light units, and a method of manufacturing the same, thevarious aspects of which are described below. Throughout the drawings,like elements are described by the same reference numeral. The drawingsare not drawn to scale. Multiple instances of an element may beduplicated where a single instance of the element is illustrated, unlessabsence of duplication of elements is expressly described or clearlyindicated otherwise. Ordinals such as “first,” “second,” and “third” areemployed merely to identify similar elements, and different ordinals maybe employed across the specification and the claims of the instantdisclosure.

As used herein, a “light emitting device” refers to any device that isconfigured to emit light and includes, but is not limited to, a lightemitting diode (LED), a laser, such as a vertical-cavitysurface-emitting laser (VCSEL), and any other electronic device that isconfigured to emit light upon application of a suitable electrical bias.A light emitting device may be a vertical structure (e.g., a verticalLED) in which the p-side and n-side contacts are located on oppositesides of the structure or a lateral structure in which the p-side andn-side contacts are located on the same side of the structure. As usedherein, a “light emitting device assembly” refers to an assembly inwhich at least one light emitting device is structurally fixed withrespect to a support structure, which can include, for example, asubstrate, a matrix, or any other structure configured to provide stablemechanical support to the at least one light emitting device.

In the present disclosure, a method is provided for transferring anarray of devices (such as an array of light emitting devices or an arrayof sensor devices) from a growth substrate to a target substrate. Thetarget substrate can be any substrate on which formation of multipletypes of devices in any configuration is desired. In an illustrativeexample, the target substrate can be a backplane substrate such as anactive or passive matrix backplane substrate for driving light emittingdevices. As used herein, a “backplane substrate” refers to any substrateconfigured to affix multiple devices thereupon. In one embodiment, thecenter-to-center spacing of neighboring light emitting devices on thebackplane substrate can be an integer multiple of the center-to-centerspacing of neighboring light emitting devices on the growth substrate.The light emitting devices may include a plurality of light emittingdevices, such as a group of two light emitting devices, one configuredto emit blue light and one configured to emit green light. The lightemitting devices may include a group of three light emitting devices,one configured to emit blue light, one configured to emit green light,and one configured to emit red light. As used herein, “neighboring lightemitting devices” refer to a plurality of two or more light emittingdevices located in closer proximity than at least another light emittingdevice. The method of the present disclosure can provide selectivetransfer of a subset of light emitting devices from a light emittingdevice array on a growth substrate to the backplane substrate.

Referring to FIG. 1, devices (10B, 10G, 10R, 10S) can be fabricated onrespective initial growth substrates (101B, 101G, 101R, 101S) employingmethods known in the art. As used herein, an “initial growth substrate”refers to a substrate that is processed to form devices thereupon ortherein. The devices (10B, 10G, 10R, 10S) can include light emittingdevices (10B, 10G, 10R) and/or sensor devices 10S (e.g., photodetectors)and/or any other electronic devices. The light emitting devices (10B,10G, 10R) can be any type of light emitting devices, i.e., verticallight emitting devices, lateral light emitting devices, or anycombination thereof. Devices of the same type can be formed on eachinitial growth substrate (101B, 101G, 101R, 101S). The devices (10B,10G, 10R, 10S) can be formed as an array on the respective initialgrowth substrates (101B, 101G, 101R, 101S).

In one embodiment, the initial growth substrates (101B, 101G, 101R,101S) can include an absorbing substrate such as a silicon substrate. Asused herein, an “absorbing substrate” refers to a substrate that absorbsmore than 50% of light energy within the spectrum range includingultraviolet range, visible range, and infrared range. As used herein,“ultraviolet range” refers to the wavelength range from 10 nm to 400 nm;“visible range” refers to the wavelength range from 400 nm to 800 nm,and “infrared range” refers to the wavelength range from 800 nm to 1 mm.

If the initial growth substrates (101B, 101G, 101R, 101S) are absorbingsubstrates, each array of devices (10B, 10G, 10R, 10S) can betransferred to a respective transparent carrier substrates, or a“transparent substrate,” by full wafer transfer processes in which eacharray of devices (10B, 10G, 10R, 10S) is transferred to the respectivetransparent substrate in its entirety. As used herein, a “transparentsubstrate” refers to a substrate that transmits more than 50% of lightenergy at a wavelength within the spectrum range including ultravioletrange, visible range, and infrared range.

In one embodiment, devices (10B, 10G, 10R, 10S) can include lightemitting devices (10B, 10G, 10R). In one embodiment, each light emittingdevice (10B, 10G, 10R) can be configured to emit light of a single peakwavelength. It is understood that light emitting devices typically emitlight of a narrow wavelength band centered around the single wavelengthat which the intensity of light is at a maximum, and the wavelength of alight emitting device refers to the peak wavelength. For example, anarray of first light emitting devices 10B can be formed on a first-typegrowth substrate 100B, an array of second light emitting devices 10G canbe formed on a second-type growth substrate 100G, and an array of thirdlight emitting devices 10R can be formed on a third-type growthsubstrate 100R. In addition, an array of sensor devices 10S can beformed on a fourth-type growth substrate 100S. Alternatively, one ormore types of light emitting devices (10B, 10G, 10R) can be integratedlight emitting devices that are configured to emit light of at least twodifferent wavelengths. In one embodiment, the light emitting devices(10B, 10G, 10R) may comprise arrays of nanowires or othernanostructures.

Contact structures (not explicitly shown) such as contact pads areprovided on each light emitting device (10B, 10G, 10R). The contactstructures for each light emitting device (10B, 10G, 10R) can include ananode contact structure and a cathode contact structure. In case one ormore of the light emitting devices (10B, 10G, 10R) is an integratedlight emitting device configured to emit light of at least two differentwavelengths, a common contact structure (such as a common cathodecontact structure) can be employed. For example, a triplet of blue,green, and red light emitting devices embodied as a single integratedlight emitting device may have a single cathode contact.

The array of light emitting devices (10B, 10G, 10R) on each initialgrowth substrate (101B, 101G, 101R) is configured such that thecenter-to-center spacing of light emitting devices on a backplanesubstrate to which the light emitting devices are subsequentlytransferred is an integer multiple of the center-to-center spacing oflight emitting devices (10B, 10G, 10R) on the initial growth substrate(101B, 101G, 101R).

Each initial growth substrate (101B, 101G, 101R, 101S) and devices (10B,10G, 10R, 10S) thereupon can be diced into suitable sizes. Each dicedportion of the initial growth substrate (101B, 101G, 101R, 101S) isherein referred to as a growth substrate (100B, 100G, 100R, 100S).Assemblies of growth substrates (100B, 100G, 100R, 100S) with respectivedevices (10B, 10G, 10R, 10S) thereupon are thus generated. In otherwords, the growth substrates (100B, 100G, 100R, 100S) are either theentirety or the diced portions of the initial growth substrates (101B,101G, 101R, 101S), and an array of devices (10B, 10G, 10R, 10S) ispresent on each growth substrate (100B, 100G, 100R, 100S). The array ofdevices (10B, 10G, 10R, 10S) on each growth substrate (100B, 100G, 100R,100S) can be an array of devices of the same type.

Prior to, or after, each initial growth substrate (101B, 101G, 101R,101S) is singulated to corresponding growth substrates (100B, 100G,100R, 100S), each device (10B, 10G, 10R, 10S), e.g., a light emittingdevice, a group of light emitting devices, or a sensor device, can bemechanically isolated from one another by forming trenches between eachneighboring pair of the devices. In an illustrative example, if a lightemitting device array or a sensor array is disposed on an initial growthsubstrate (101B, 101G, 101R, 101S), the trenches can extend from thefinal growth surface of the light emitting device array or the sensorarray to the top surface of the initial growth substrate (101B, 101G,101R, 101S).

Various schemes may be employed to transfer each array of devices (10B,10G, 10R, 10S) to a respective transparent substrate, which is hereinreferred to as a transfer substrate. FIGS. 2-6 illustrate an exemplaryscheme that can be employed to transfer each array of devices (10B, 10G,10R, 10S) to a respective transparent substrate.

Referring to FIG. 2, first carrier substrates 200 can be optionallyemployed in case the contact structures on each device (10B, 10G, 10R,10S) are formed on the top side of each device (10B, 10G, 10R, 10S)during fabrication of the devices (10B, 10G, 10R, 10S) on the growthsubstrates (101B, 101G, 101R, 101S). The first carrier substrates 200can be any suitable substrate that can be bonded to the devices (10B,10G, 10R, 10S) and can provide structural support to the (10B, 10G, 10R,10S). Each as-grown array of devices (10B, 10G, 10R, 10S) and arespective growth substrate 100 is bonded to a first carrier substrate200. Thus, each growth substrate 100 can be bonded to a respective firstcarrier substrate 200 through the respective devices 10. In other words,the devices 10 are present between a growth substrate 100 and a firstcarrier substrate within each bonded structure (100, 10, 200). In anillustrative example, a first-type growth substrate 100B can be bondedto a first-type first carrier substrate 200B through first lightemitting devices 10B, a second-type growth substrate 100G can be bondedto a second-type first carrier substrate 200G through second lightemitting devices 10G, a third-type growth substrate 100R can be bondedto a third-type first carrier substrate 200R through third lightemitting devices 10R, and a fourth-type growth substrate 100S can bebonded to a fourth-type first carrier substrate 200S through the sensordevices 10S.

Referring to FIG. 3, each growth substrate 100 can be removed from thetransient bonded structure including the stack of the growth substrate100, an array of devices 10, and the first carrier substrate 200. Forexample, if the growth substrate 100 is a silicon substrate, the growthsubstrate 100 can be removed by a wet chemical etch process, grinding,polishing, splitting (for example, at a hydrogen implanted layer), or acombination thereof. For example, splitting of a substrate can beperformed by implanting atoms that form a weak region (such as hydrogenatoms implanted into a semiconductor material) and by applying asuitable processing conditions (for example, an anneal at an elevatedtemperature and/or mechanical force) to cause the substrate to splitinto two parts.

Referring to FIG. 4, a first bonding material layer 30A can be formed oneach first carrier substrate 200. The first bonding material layer 30Aincludes any bonding material that can be bonded to another bondingmaterial upon suitable treatment (such as application of heat and/orpressure). In one embodiment, the first bonding material layer 30A cancomprise a dielectric material such as silicon oxide,borophosphosilicate glass (BPSG), a spin-on glass (SOG) material, and/oran adhesive bonding material such as SU-8 or benzocyclobutene (BCB). Thethickness of the first bonding material layer 30A can be in a range from50 nm to 5 micron, although lesser and greater thicknesses can also beemployed. In one embodiment, the first bonding material layer 30A can bea silicon oxide layer having a thickness of about 1 micron. The firstbonding material layer 30A can be formed by a suitable deposition methodsuch as chemical vapor deposition or spin coating.

Transfer substrates 300 are provided. As used herein, a “transfersubstrate” refers to a substrate from which at least one device istransferred to a target substrate, which can comprise a backplanesubstrate. In one embodiment, each transfer substrate 300 can be asecond carrier substrate, which can be employed to receive an array ofdevices from a respective first carrier substrate 200 and to carry thearray of devices until a subset of the devices are transferred to thetarget substrate in a subsequent process.

In some embodiments, the transfer substrates 300 can be opticallytransparent at a laser wavelength. The laser wavelength is thewavelength of the laser beam to be subsequently employed to transferdevices individually and selectively from a respective transfersubstrate 300 to the target substrate, and can be an ultravioletwavelength, a visible wavelength, or an infrared wavelength. In oneembodiment, the transparent substrates 300 can include sapphire, glass(silicon oxide), or other optically transparent material known in theart. In an alternative embodiment, the transfer substrates 300 can betransparent growth substrates or diced portions thereof. In some otherembodiments in which initial growth substrates are cleaved (for example,at a layer implanted with hydrogen or noble gas) to provide a thinsubstrate from which light emitting diodes are transferred to abackplane without use of transfer substrates, the initial growthsubstrates may absorb laser at the laser wavelength.

A release layer 20 and a second bonding material layer 30B can besequentially deposited on each transfer substrate 300. The release layer20 includes a material that can provide sufficient adhesion to thetransfer substrate 300 and is absorptive at the laser wavelength of thelaser beam to be subsequently employed during a subsequent selectivetransfer process. For example, the release layer 20 can includesilicon-rich silicon nitride or a semiconductor layer, such as a GaNlayer that can be heated by laser irradiation. The thickness of therelease layer 20 can be in a range from 100 nm to 1 micron, althoughlesser and greater thicknesses can also be employed.

The second bonding material layer 30B can comprise a dielectric materialsuch as silicon oxide. The thickness of the second bonding materiallayer 30B can be in a range from 50 nm to 5 micron, although lesser andgreater thicknesses can also be employed. In one embodiment, the secondbonding material layer 30B can be a silicon oxide layer having athickness of about 1 micron. The second bonding material layer 30B canbe formed by a suitable deposition method such as chemical vapordeposition or spin coating.

A transfer substrate 300 can be provided for each first carriersubstrate 200. For example, a first transfer substrate 300B can beprovided for the first-type first carrier substrate 200B; a secondtransfer substrate 300G can be provided for the second-type firstcarrier substrate 200G; a third transfer substrate 300R can be providedfor the third-type first carrier substrate 300R; and an additionaltransfer substrate 300S can be provided for the additional type firstcarrier substrate 300S. Multiple stacked structures can be formed, whichinclude a first stacked structure (300B, 20, 30B) including a stack ofthe first transfer substrate 300B, a release layer 20, and a secondbonding material layer 30B; a second stacked structure (300G, 20, 30B)including a stack of the second transfer substrate 300G, a release layer20, and a second bonding material layer 30B; a third stacked structure(300R, 20, 30B) including a stack of the third transfer substrate 300R,a release layer 20, and a second bonding material layer 30B; and anadditional stacked structure (300S, 20, 30B) including a stack of theadditional transfer substrate 300S, a release layer 20, and a secondbonding material layer 30B.

The combination of the array of first light emitting devices 10B and thefirst transfer substrate 300B is herein referred to as a first transferassembly (300B, 10B), the combination of the second light emittingdevices 10G and the second transfer substrate 300G is herein referred toas a second transfer assembly (300G, 10G), and the combination of thethird light emitting devices 10R and the third transfer substrate 300Ris herein referred to as a third transfer assembly (300R, 10R). Inaddition, the combination of the sensor devices 10S and the fourthtransfer substrate 300S is herein referred to as fourth transferassembly (300S, 10S).

Referring to FIG. 5, each pair of a first carrier substrate 200 and atransfer substrate 300 (which can be a second carrier substrate) can bebonded. For example, the second bonding material layer 30B can be bondedwith the respective first bonding material layer 30A on thecorresponding first carrier substrate 200 to form a bonding materiallayer 30. Each bonded assembly comprises a first transfer substrate 300,a release layer 20, a bonding material layer 30, and an array of devices10.

Referring to FIG. 6, a first carrier substrate 200 is removed from eachbonded assembly (300, 20, 30, 200), for example, by polishing, grinding,cleaving, and/or chemical etching. Each array of devices 20 can bedisposed on a transfer substrate 300, which is a transparent carriersubstrate with a release layer 20 thereupon, i.e., between thetransparent carrier substrate and the array of devices 20.

Referring to FIG. 7, each array of devices 10 on a respective transfersubstrate 300 can be arranged such that each device 10 is laterallyspaced from neighboring devices 10 by trenches. For example, the arrayof first light emitting devices 10B on the first transfer substrate 300Bcan be laterally spaced from one another by trenches. Optionally, afirst optical protection material layer 17B can be applied to fill thegaps among the first light emitting devices 10B. Similarly, an opticalprotection material layer can be applied to fill the gaps among eacharray of devices 10 on other transfer substrates (300G, 300R, 300S).Each optical protection material layer comprises a material that absorbsor scatters light at the laser wavelength of the laser beam to besubsequently employed. Each optical protection material layer caninclude, for example, silicon-rich silicon nitride, an organic orinorganic antireflective coating (ARC) material, or a photoresistmaterial. Each optical protection material layer can be formed such thatthe outside surfaces of the devices 10 are not covered by the opticalprotection material layer. The optical protection material layers can beformed, for example, by spin coating or by a combination of depositionand a recess etch.

Each assembly (300, 20, 30, 10) comprising a transfer substrate 300 andan array of devices 10 can further comprise a release layer 20contacting the respective transfer substrate 300 and comprising amaterial that absorbs light at a wavelength selected from ultravioletrange, visible range, and infrared range, and a bonding material layer30 contacting the release layer 20 and the respective array of devices10.

FIGS. 7A-7E illustrate sequential schematic top-down views of multiplesupply coupons and multiple backplanes during an exemplary transfersequence for transferring four different types of devices (10B, 10G,10R, 10S) (e.g., blue, green and red emitting LEDs and sensors,respectively) to four backplanes (401, 402, 403, 404). FIGS. 8A-8Xillustrate vertical cross-sectional views of a first backplane andvarious structures disposed thereupon.

Referring to FIG. 7A, exemplary device-side bonding structure patternsfor a set of source coupons and bonding sites on correspondingbackplanes (401, 402, 403, 404) are illustrated. The four differenttypes of devices (10B, 10G, 10R, 10S) can be provided on four sourcesubstrates (301B, 301G, 301R, 301S), which can comprise four transfersubstrates (301B, 301G, 301R, 301S), or four growth substrates (100B,100G, 100R, 100S), or combinations thereof. First devices 10B of a firsttype can be provided on the first source 301B, second devices 10G of asecond type can be provided on the second source 301G, third devices 10Rof a third type can be provided on the third source 301R, and fourthdevices 10S of a fourth type can be provided on the fourth source 301S.In one embodiment, the first devices 10B can be light emitting devicesthat emit light at a first wavelength (i.e., a light spectrum having anintensity peak at the first wavelength), the second devices 10G can belight emitting devices that emit light at a second wavelength, the thirddevices 10R can be light emitting devices that emit light at a thirdwavelength, and the fourth devices 10S can be semiconductor sensordevices.

The source substrates (301B, 301G, 301R, 301S) can be aligned to thebackplanes (401, 402, 403, 404) prior to transfer of the various subsetof devices (10B, 10G, 10R, 10S). FIG. 8A illustrates a verticalcross-sectional view of through the first backplane 401 and the firstsource substrate 301B after alignment. The zig-zag plane of the verticalcross-sectional view of FIG. 8A are shown in FIG. 7A. The verticalcross-sectional view of the first backplane 401 is illustrative of thesecond, third, and fourth backplanes (402, 403, 404). In other words,processes performed on the second, third, and fourth backplanes (402,403, 404) can be substantively equivalent to the processes performed onthe first backplane mutatis mutandis in a manner consistent with theconfiguration illustrated in FIG. 7A.

Each of the backplanes (401, 402, 403, 404) (such as the first backplane401) includes a periodic array of multiple instances of a backplane-sideunit cell structure U that comprises a set of backplane-side bondingstructures 14 including a common metal. The common metal is an elementalmetal that provides multiple eutectic systems with different metals.

Different types of device-side bonding structures (121, 122, 123, 124)can be formed on the entirety of the devices on each source substrate(301B, 301G, 301R, or 301S). The number of types of device-side bondingstructures (121, 122, 123, 124) can be the same as the number ofbackplanes (401, 402, 403, 404) that are employed for transfer of thedevices (10B, 10G, 10R, 10S). In one embodiment, a two-dimensional arrayof instances of a first unit cell structure U1 can be provided onsurfaces of the first devices 10B that are distal from the first sourcesubstrate 301. The first unit cell structure U1 can include an instanceof a first device-side bonding structure 121, an instance of a seconddevice-side bonding structure 122, an instance of a third device-sidebonding structure 123, and an instance of a fourth device-side bondingstructure 124.

Instances of the first unit cell structure U1 are repeated on the firstsource substrate 301B to form a two-dimensional array having atwo-dimensional periodicity. Instances of the second unit cell structureU2 are repeated on the second source substrate 301G to form atwo-dimensional array having the two-dimensional periodicity. Instancesof the third unit cell structure U1 are repeated on the third sourcesubstrate 301R to form a two-dimensional array having thetwo-dimensional periodicity. Instances of the fourth unit cell structureU1 are repeated on the fourth source substrate 301S to form atwo-dimensional array having the two-dimensional periodicity.

Each instance of a unit cell structure (U1, U2, U3, or U4) can include aplurality of devices of the same type, which can be the first devices10B, the second devices 10G, the third devices 10R, or the fourthdevices 10S. The number of the devices in each unit cell structure (U1,U2, U3, U4) can be the same as the number of the backplanes (401, 402,403, 404), which is four in the illustrative example. Each instance of aunit cell structure (U1, U2, U3, or U4) can include multiple device-sidebonding structures (121, 122, 123, 124) of different types, which mayinclude a first device-side bonding structure 121, a second device-sidebonding structure 122, a third device-side bonding structure 123, and afourth device-side bonding structure 124.

In one embodiment, each instance of the first device-side bondingstructure 121 can include a first metal that forms a first eutectic witha metal in target-side bonding structures 14 that are provided on thebackplanes (401, 402, 403, 404) at a first eutectic temperature. Eachinstance of the second device-side bonding structure 122 can include asecond metal that forms a second eutectic with the metal in target-sidebonding structures 14 that are provided on the backplanes (401, 402,403, 404) at a second eutectic temperature. Each instance of the thirddevice-side bonding structure 123 can include a third metal that forms athird eutectic with the metal in target-side bonding structures 14 thatare provided on the backplanes (401, 402, 403, 404) at a third eutectictemperature. Each instance of the fourth device-side bonding structure124 can include a fourth metal that forms a fourth eutectic with themetal in target-side bonding structures 14 that are provided on thebackplanes (401, 402, 403, 404) at a fourth eutectic temperature. Thefirst metal, the second metal, the third metal, and the fourth metal canbe different from one another. In one embodiment, the second eutectictemperature can be higher than the first eutectic temperature, the thirdeutectic temperature can be higher than the second eutectic temperature,and the fourth eutectic temperature can be higher than the thirdeutectic temperature.

A periodic array of multiple instances of a backplane-side unit cellstructure UT can be provided on a surface of each backplane (401, 402,403, 404). In one embodiment, the array of multiple instances of abackplane-side unit cell structure UT can be a two-dimensionalrectangular periodic array in which the multiple instances of thebackplane-side unit cell structure UT are repeated in two orthogonaldirections that are perpendicular to a surface of a respective backplane(401, 402, 403, 404). In one embodiment, each instance of thebackplane-side unit cell structure UT can include a plurality of bondingstructures configured to mate with each type of device-side bondingstructures (121, 122, 123, 124). In an illustrative example, eachinstance of the backplane-side unit cell structure UT can include abonding structure configured to mate with a first device-side bondingstructure 121, a second device-side bonding structure 122, a thirddevice-side bonding structure 123, and a fourth device-side bondingstructure 124. In one embodiment, the number of bonding structures ineach backplane-side unit cell structure UT can be the same as the numberof types of the devices (10B, 10G, 10R, 10S) to be transferred to therespective backplane (401, 402, 403, 404). In one embodiment, eachbackplane-side bonding structure 14 on the backplanes (401, 402, 403,404) can include a common metal that forms eutectics with each metal ofthe device-side bonding structures (121, 122, 123, 124), i.e., with eachof the first, second, third, and fourth metals.

In one embodiment, each backplane-side bonding structure 14 on thebackplanes (401, 402, 403, 404) can be a bond pad structure having arespective planar surface. In one embodiment, each instance of the firstdevice-side bonding structure 121, the second device-side bondingstructure 122, the third device-side bonding structure 123, and thefourth device-side bonding structure 124 can be a bond pad structurehaving a respective planar surface configured to mate with an instanceof the backplane-side bonding structure 14.

In one embodiment, the first unit cell structure U1 can include multiplefirst devices 10B, i.e., at least two first devices 10B such as three,four, five, or six first devices. An instance of the first device-sidebonding structure 121 can be provided on one of the multiple firstdevices 10B in the first unit cell structure U1, and an instance of thesecond device-side bonding structure 122 can be provided on another ofthe multiple first devices 10B in the first unit cell structure U1.Additionally, an instance of the third device-side bonding structure 123can be provided on yet another of the multiple first devices 10B in thefirst unit cell structure U1. Additionally, an instance of the fourthdevice-side bonding structure 124 can be provided on still another ofthe multiple first devices 10B in the first unit cell structure U1.

Additionally, the second unit cell structure U2 can include multiplesecond devices 10G, i.e., at least two second devices 10G such as three,four, five, or six first devices. An instance of the first device-sidebonding structure 121 can be provided on one of the multiple seconddevices 10G in the second unit cell structure U2, and an instance of thesecond device-side bonding structure 122 can be provided on another ofthe multiple second devices 10G in the second unit cell structure U2.Additionally, an instance of the third device-side bonding structure 123can be provided on yet another of the multiple second devices 10G in thesecond unit cell structure U2. Additionally, an instance of the fourthdevice-side bonding structure 124 can be provided on still another ofthe multiple second devices 10G in the second unit cell structure U2.

Additionally, the third unit cell structure U3 can include multiplethird devices 10R, i.e., at least two third devices 10R such as three,four, five, or six first devices. An instance of the first device-sidebonding structure 121 can be provided on one of the multiple thirddevices 10R in the third unit cell structure U3, and an instance of thesecond device-side bonding structure 122 can be provided on another ofthe multiple third devices 10R in the third unit cell structure U3.Additionally, an instance of the third device-side bonding structure 123can be provided on yet another of the multiple third devices 10R in thethird unit cell structure U3. Additionally, an instance of the fourthdevice-side bonding structure 124 can be provided on still another ofthe multiple third devices 10R in the third unit cell structure U3.

Additionally, the fourth unit cell structure U4 can include multiplefourth devices 10S, i.e., at least two fourth devices 10S such as three,four, five, or six first devices. An instance of the first device-sidebonding structure 121 can be provided on one of the multiple fourthdevices 10S in the fourth unit cell structure U4, and an instance of thesecond device-side bonding structure 122 can be provided on another ofthe multiple fourth devices 10S in the fourth unit cell structure U4.Additionally, an instance of the third device-side bonding structure 123can be provided on yet another of the multiple fourth devices 10S in thefourth unit cell structure U4. Additionally, an instance of the fourthdevice-side bonding structure 124 can be provided on still another ofthe multiple fourth devices 10S in the fourth unit cell structure U4.

Each instance of the first device-side bonding structure 121, the seconddevice-side bonding structure 122, the third device-side bondingstructure 123, and the fourth device-side bonding structure 124 can be abond pad structure having a respective planar surface configured to matewith an instance of the backplane-side bonding structure 14.

Generally, the first source coupon (301B, 10B) can include a firstsource substrate 301R and a periodic array of multiple instances of afirst unit cell structure U1 that comprises at least one first device10B (such as multiple first devices 10B) and having a same periodicityas the periodic array of multiple instances of the backplane-side unitcell structure UT. An instance of the first device-side bondingstructure 121 including the first metal can be provided on one firstdevice 10B per each first unit cell structure U1, and the common metaland the first metal are selected to provide a first bonding metallurgyhaving the first eutectic temperature upon bonding in a subsequentprocess.

The second source coupon (301G, 10G) can include a second sourcesubstrate 301G and a periodic array of multiple instances of a secondunit cell structure U2 that comprises at least one second device 10G andhaving the same periodicity as the periodic array of multiple instancesof the backplane-side unit cell structure UT. An instance of the seconddevice-side bonding structure 122 including the second metal is providedon one second device 10G per each second unit cell structure U2, and thecommon metal and the second metal are selected to provide a secondbonding metallurgy having a second eutectic temperature upon bonding.The second eutectic temperature is greater than the first eutectictemperature.

The third source coupon (301R, 10R) can include a third source substrate301R and a periodic array of multiple instances of a third unit cellstructure U3 that comprises at least one third device 10R and having thesame periodicity as the periodic array of multiple instances of thebackplane-side unit cell structure UT. An instance of the thirddevice-side bonding structure 123 including the third metal is providedon one third device 10R per each third unit cell structure U3, and thecommon metal and the third metal are selected to provide a third bondingmetallurgy having a third eutectic temperature upon bonding. The thirdeutectic temperature is greater than the second eutectic temperature.

The fourth source coupon (301S, 10S) can include a fourth sourcesubstrate 301S and a periodic array of multiple instances of a fourthunit cell structure U4 that comprises at least one fourth device 10S andhaving the same periodicity as the periodic array of multiple instancesof the backplane-side unit cell structure UT. An instance of the fourthdevice-side bonding structure 124 including the fourth metal is providedon one fourth device 10S per each fourth unit cell structure U4, and thecommon metal and the fourth metal are selected to provide a fourthbonding metallurgy having a fourth eutectic temperature upon bonding.The fourth eutectic temperature is greater than the first, second, andthird eutectic temperatures.

Referring to FIG. 8B, each source coupon (301B, 301G, 301R, 301S) and arespective backplane (401, 402, 403, 404) are brought into contact witheach other such that each device-side bonding structure (121, 122, 123,124) contacts a mating backplane-side bonding structure 14. In anillustrative example, the first source coupon 301B can contact the firstbackplane 401 through vertically stacked pairs of a device-side bondingstructure (121, 122, 123, 124) and a mating backplane-side bondingstructure 14. The second source coupon 301B can contact the secondbackplane 401 through vertically stacked pairs of a device-side bondingstructure (121, 122, 123, 124) and a mating backplane-side bondingstructure 14. The third source coupon 301B can contact the thirdbackplane 401 through vertically stacked pairs of a device-side bondingstructure (121, 122, 123, 124) and a mating backplane-side bondingstructure 14. The fourth source coupon 301B can contact the fourthbackplane 401 through vertically stacked pairs of a device-side bondingstructure (121, 122, 123, 124) and a mating backplane-side bondingstructure 14.

Referring to FIGS. 7B and 8C, the mated pairs of a source coupon (301B,301G, 301R, 301S) and a respective backplane (401, 402, 403, 404) areannealed at a first anneal temperature, which is at, or greater than,the first eutectic temperature at which the combination of the commonmetal in the backplane-side bonding structures 14 and the first metal inthe first device-side bonding structures 121 form a eutectic compoundand reflowed to form first bonded solder material portions 161.

In an illustrative example, devices (10B, 10G, 10R, 10S) that are markedwith “1” are provided with a respective first device-side bondingstructure 121, and thus, are bonded to the respective backplane (401,402, 403, 404). Devices (10B, 10G, 10R, 10S) that are marked with “2,”“3,” or “4” are provided with a respective second, third, or fourthdevice-side bonding structure (122, 123, 124), and thus, are not bondedto any backplane (401, 402, 403, 404).

In one embodiment, one first device 10B from each instance of the firstunit cell structure U1 can be transferred to the first backplane 401 bybonding respective instances of the first device-side bonding structure121 to matching backplane-side bonding structures 14. A periodic arrayof first bonded solder material portions 161 having the first bondingmetallurgy is formed while backplane-side bonding structures 14 that arenot bonded do not reflow. First devices 10B provided with respectiveinstances of the second, third, or fourth device-side bonding structure(122, 123, or 124) are not transferred to the first backplane 401 duringtransfer of the first devices 10B provided with respective instances ofthe first device-side bonding structure 121. Instances of the second,third, and fourth device-side bonding structures on the first devices10B on the first source substrate 301B are in physical contact withrespective backplane-side bonding structure 14 without reflowing duringtransfer of the first devices 10B provided with respective instances ofthe first device-side bonding structure 121 to the first backplane 401.

Similarly, the second devices 10G provided with the first device-sidebonding structures 121 can be bonded to the second backplane 402, whilethe second devices 10G provided with the second, third, or fourthdevice-side bonding structures (122, 123, 124) are not bonded to thesecond backplane 402. The third devices 10R provided with the firstdevice-side bonding structures 121 can be bonded to the third backplane403, while the third devices 10R provided with the second, third, orfourth device-side bonding structures (122, 123, 124) are not bonded tothe third backplane 403. The fourth devices 10S provided with the firstdevice-side bonding structures 121 can be bonded to the fourth backplane404, while the fourth devices 10S provided with the second, third, orfourth device-side bonding structures (122, 123, 124) are not bonded tothe fourth backplane 404.

Referring to FIG. 8D, an alternative method can be employed to bond thedevices with an instance of the first device-side bonding structure 121to respective backplanes (401, 402, 403, 404). Specifically, the devices(10B, 10G, 10R, 10S) with a respective first bonded material portion 12thereupon can be bonded to a respective second bonded material portion14 by sequentially reflowing respective at least one solder materialportion (within the vertical stacks of a first device-side bondingstructure 121 and a backplane-side bonding structure 14. In oneembodiment, the reflowing of the solder material portions can beperformed by irradiating a laser beam on each solder material pads to bereflowed. The laser beam can be provided by a laser 377. The wavelengthof the laser beam can be selected such that the laser beam passesthrough the respective source substrate (301B, 301G, 301R, 301S) and therespective devices (10B, 10G, 10R, 10S). In one embodiment, thewavelength of the laser beam can be in a visible light range (i.e., awavelength range from 400 nm to 800 nm) or in the infrared range (i.e.,wavelength range from 800 nm to 1 mm).

A first bonded solder material portion 161 is formed by reflow of eachsolder material underlying the bonded devices (10B, 10G, 10R, 10S). Eachfirst bonded solder material portion 161 includes a reflowed andre-solidified solder material and additionally includes a pair of metalpads (not separately shown) that are attached to the respectivebackplane (401, 402, 403, 404) and a respective device (10B, 10G, 10R,10S).

Referring to FIG. 8E, each bonded device (10B, 10G, 10R, 10S) can bedetached from a respective source substrate (301B, 301G, 301R, 301S). Inone embodiment, each source substrate (301B, 301G, 301R, 301S) cancomprises a bulk material portion (e.g., a transfer substrate 300) thatis transparent to the laser beam and adjoined to at least one surfaceportion (such as the release layer 20 and the bonding material layer 30)of the source substrate (301B, 301G, 301R, 301S). The laser beam can beprovided by a laser 477. In one embodiment, the laser beam can passthrough the bulk material portion prior to impinging on the at least onesurface portion of the source substrate (301B, 301G, 301R, 301S).

In one embodiment, the laser beam can ablate each surface portion of thesource substrate (301B, 301G, 301R, 301S) that is proximal to the bondeddevices (10B, 10G, 10R, 10S). In one embodiment, surface portions of thesource substrate (301B, 301G, 301R, 301S) that are proximal to thebonded devices (10B, 10G, 10R, 10S) can comprise a release layer 20. Inone embodiment, the release layer can include silicon nitride or asemiconductor material (such as GaN) that is ablated upon absorption ofthe laser beam. In this case, the laser wavelength can be an ultravioletwavelength (such as 248 nm or 193 nm), and irradiating the surfaceportions of the source substrate 301 with the laser beam can ablate thesurface portions.

Referring to FIG. 8F, the source substrates (301B, 301G, 301R, 301S) andthe devices (10B, 10G, 10R, 10S) that are not bonded to the backplanes(401, 402, 403, 404) are separated from each combination of a backplane(401, 402, 403, 404) and bonded devices (10B, 10G, 10R, 10S) thereupon.

Referring to FIG. 7C, the source coupons and the backplanes are matchedso that the next sets of devices to be transferred are matched to thetarget bonding sites. The processing steps of FIGS. 8G, 8H, 8I, 8K, and8L or the processing steps of FIGS. 8G, 8H, 8J, 8K, and 8L aresequentially formed to transfer the next sets of devices to therespective backplanes (401, 402, 403, 404). Processing step in FIGS.8G-8L may employ the same methods as the processing steps of FIGS. 8A-8Fmutatis mutandis. The devices labeled “2” are transferred to therespective backplanes (401, 402, 403, 404) through the processing stepsof FIGS. 8G-8L. The sequence of processing steps may be performed forthe pair of first source coupon (301B, 10B) and the second backplane402, for the pair of the second source coupon (301G, 10G) and the firstbackplane 401, for the pair of the third source coupon (301R, 10R) andthe fourth backplane 404, and for the pair of the fourth source coupon(301S, 10S) and the third backplane 403. It is understood that thesource coupons and/or the backplanes may be aligned to avoid collisionbetween previously bonded devices and devices in a newly disposed sourcecoupon.

The bonding processes of FIG. 8I or 8J are modified to induce bonding ofeach vertically contacting pair of a second device-side bondingstructure 122 and a backplane-side bonding structure 14. In oneembodiment, one second device 10G from each instance of the second unitcell structure U2 can be transferred to the first backplane 401 bybonding respective instances of the second device-side bonding structure122 to matching backplane-side bonding structures 14. A periodic arrayof second bonded material portions 162 having the second bondingmetallurgy is formed while backplane-side bonding structures 14 that arenot bonded do not reflow. Second devices 10G provided with respectiveinstances of the third or fourth device-side bonding structure (123, or124) are not transferred to the first backplane 401 during transfer ofthe second devices 10G provided with respective instances of the seconddevice-side bonding structure 122. Instances of the third and fourthdevice-side bonding structures (123, 124) on the second devices 10G onthe first source substrate 301B are in physical contact with respectivebackplane-side bonding structure 14 without reflowing during transfer ofthe second devices 10B provided with respective instances of the seconddevice-side bonding structure 122 to the first backplane 401.

Referring to FIG. 7D, the source coupons and the backplanes are matchedso that the next sets of devices to be transferred are matched to thetarget bonding sites. The processing steps of FIGS. 8M, 8N, 8O, 8Q, and8R or the processing steps of 8M, 8N, 8P, 8Q, and 8R are sequentiallyformed to transfer the next sets of devices to the respective backplanes(401, 402, 403, 404). Processing step in FIGS. 8M-8R may employ the samemethods as the processing steps of FIGS. 8A-8F mutatis mutandis. Thedevices labeled “3” are transferred to the respective backplanes (401,402, 403, 404) through the processing steps of FIGS. 8M-8R. The sequenceof processing steps may be performed for the pair of first source coupon(301B, 10B) and the third backplane 403, for the pair of the secondsource coupon (301G, 10G) and the fourth backplane 404, for the pair ofthe third source coupon (301R, 10R) and the first backplane 401, and forthe pair of the fourth source coupon (301S, 10S) and the secondbackplane 402. It is understood that the source coupons and/or thebackplanes may be aligned to avoid collision between previously bondeddevices and devices in a newly disposed source coupon.

The bonding processes of FIG. 8I or 8J are modified to induce bonding ofeach vertically contacting pair of a third device-side bonding structure123 and a backplane-side bonding structure 14. In one embodiment, onethird device 10R from each instance of the third unit cell structure U3can be transferred to the first backplane 401 by bonding respectiveinstances of the third device-side bonding structure 123 to matchingbackplane-side bonding structures 14. A periodic array of third bondedmaterial portions 163 having the third bonding metallurgy is formedwhile backplane-side bonding structures 14 that are not bonded do notreflow. Third devices 10R provided with respective instances of thefourth device-side bonding structure 124 are not transferred to thefirst backplane 401 during transfer of the third devices 10R providedwith respective instances of the third device-side bonding structure123. Instances of the fourth device-side bonding structures 124 on thethird devices 10R on the first source substrate 301B are in physicalcontact with respective backplane-side bonding structure 14 withoutreflowing during transfer of the third devices 10B provided withrespective instances of the third device-side bonding structure 123 tothe first backplane 401.

Referring to FIG. 7E, the source coupons and the backplanes are matchedso that the next sets of devices to be transferred are matched to thetarget bonding sites. The processing steps of FIGS. 8S, 8T, 8U, 8W, and8X or the processing steps of 8S, 8T, 8V, 8W, and 8X are sequentiallyformed to transfer the next sets of devices to the respective backplanes(401, 402, 403, 404). Processing step in FIGS. 8S-8X may employ the samemethods as the processing steps of FIGS. 8A-8F mutatis mutandis. Thedevices labeled “4” are transferred to the respective backplanes (401,402, 403, 404) through the processing steps of FIGS. 8S-8X. The sequenceof processing steps may be performed for the pair of first source coupon(301B, 10B) and the fourth backplane 404, for the pair of the secondsource coupon (301G, 10G) and the third backplane 403, for the pair ofthe third source coupon (301R, 10R) and the second backplane 402, andfor the pair of the fourth source coupon (301S, 10S) and the firstbackplane 401. It is understood that the source coupons and/or thebackplanes may be aligned to avoid collision between previously bondeddevices and devices in a newly disposed source coupon.

The bonding processes of FIG. 8I or 8J are modified to induce bonding ofeach vertically contacting pair of a fourth device-side bondingstructure 124 and a backplane-side bonding structure 14. In oneembodiment, one fourth device 10S from each instance of the fourth unitcell structure U4 can be transferred to the first backplane 401 bybonding respective instances of the fourth device-side bonding structure124 to matching backplane-side bonding structures 14. A periodic arrayof fourth bonded material portions 164 having the fourth bondingmetallurgy is formed.

The device assemblies including any of the backplanes (401, 402, 403,404) as illustrated in FIGS. 7E and 8X can include a periodic array ofmultiple instances of a unit cell structure. Each instance of the unitcell structure UC comprises a first device 10B bonded to the backplane(401, 402, 403, or 402) through a first bonded material portion 161employing a first bonding metallurgy, a second device 10G bonded to thebackplane (401, 402, 403, or 402) through a second bonded materialportion 162 employing a second bonding metallurgy, a third device 10Rbonded to the backplane (401, 402, 403, or 402) through a third bondedmaterial portion 163 employing a third bonding metallurgy, and a fourthdevice 10S bonded to the backplane (401, 402, 403, or 402) through afourth bonded material portion 164 employing a fourth bondingmetallurgy.

In one embodiment, the first bonding metallurgy, the second bondingmetallurgy, the third bonding metallurgy, and the fourth bondingmetallurgy can include a common metal. The first bonding metallurgy caninclude a first metal that is not present in the second, third, andfourth bonding metallurgies. The second bonding metallurgy can include asecond metal that is not present in the first, third, and fourth bondingmetallurgies. The third bonding metallurgy can include a third metalthat is not present in the first, second, and fourth bondingmetallurgies. The fourth bonding metallurgy can include a fourth metalthat is not present in the first, second, and third bondingmetallurgies.

In an illustrative example, the first device 10B may be a first lightemitting device that emits light with a peak intensity at a firstwavelength, the second device 10G may be a second light emitting devicethat emits light with a peak intensity at a second wavelength that isdifferent from the first wavelength, the third device 10R may be a thirdlight emitting device that emits light with a peak intensity at a thirdwavelength that is different from the first and second wavelengths, andthe fourth device 10S may be a sensor semiconductor device, i.e., asemiconductor device that provides the electrical function of sensing alocal physical parameter such as a touch in a touch screen. In oneembodiment, the device assembly can be an integrated light emittingdevice assembly.

In one embodiment, the top surfaces of all instances of the first,second, third, and fourth devices (10B, 10G, 10R, 10S) on each backplane(401, 402, 403, 404) may be within a same horizontal plane, for example,by reflowing of the solder material portions (161, 162, 163, 164) at atemperature at, or greater than, the fourth eutectic temperature whilepushing the first, second, third, and fourth devices (10B, 10G, 10R,10S) toward the respective backplane (401, 402,403, 404) with a supportsubstrate having a planar surface.

The periodic array of devices (10B, 10G, 10R, 10S) as attached to abackplane (401, 402, 403, 404) can be the same as the periodicity of thebackplane-side unit cell structure UT, which is the same as theperiodicity of the first, second, third, and fourth unit structures (U1,U2, U3, U4). In one embodiment, the periodic array can be atwo-dimensional rectangular periodic array in which the multipleinstances of the unit cell structure are repeated in two orthogonaldirections that are perpendicular to a surface of the backplane to whichthe periodic array is attached.

In one embodiment, the device assembly can be an integrated lightemitting device assembly that comprises an emissive display panelcontaining light emitting diodes that emit three or more differentcolors. In one embodiment, the emissive display panel can comprise adirect view display panel containing red, green, and blue wavelengthlight emitting diodes and sensors bonded to the backplane.

The common metal for the backplane-side bonding structures can beselected from any metal that provides multiple eutectics with multiplemetals. Non-limiting exemplary combination of a common metal andmultiple metals that provide multiple eutectic systems are listed inTable 1.

TABLE 1 Examples of metals that provide multiple eutectic systems withother metals. Tin Based In Based T_(m)(Sn) = 232C T_(m)(In) =156C BinaryLowest Highest Binary Lowest Highest Au—Pd 100 Au—Pd 100 In—Sn 120 In—Sn120 Ag—In 144 205 Ag—In 144 205 Au—In 153 224 Au—In 153 224 Cu—In 153310 Cu—In 153 310 In—Pt 154 In—Pt 154 In—Pd 156 In—Pd 156 In—Te 156 418In—Te 156 418 Cu—Sn 186 227 Cu—Sn 186 227 Sn—Zn 199 Sn—Zn 199 Au—Sn 217252 Au—Sn 217 252 Ag—Sn 221 Ag—Sn 221 Al—Sn 228 Al—Sn 228 Sn—Te 228Sn—Te 228 Pd—Sn 230 Pd—Sn 230 Ge—Sn 231 Ge—Sn 231 Ni—Sn 231 Ni—Sn 231Sn—Ti 231 Sn—Ti 231 Cr—Sn 232 Cr—Sn 232 Nb—Sn 232 Nb—Sn 232 Sn—Sn 232Sn—Sn 232 Au—Cu 240 Au—Cu 240 Cu—Ni 250 350 Cu—Ni 250 350 Ag—Te 295 353Ag—Te 295 353 Cu—Te 340 Cu—Te 340 Al—Cr 350 Al—Cr 350 Au—Ge 360 Au—Ge360 Au—Si 363 Au—Si 363 Ge—Te 365 400 Ge—Te 365 400 Cu—Pd 400 Cu—Pd 400Cu—Pt 418 Cu—Pt 418 Te Based Cu Based T_(m)(Te) = 449C Eutectics & SolidState Rx Binary Lowest Highest Binary Lowest Highest Au—Pd 100 Au—Pd 100In—-Sn 120 In—Sn 120 Ag—In 144 205 Ag—In 144 205 Au—In 153 224 Au—In 153224 Cu—In 153 310 Cu—In 153 310 In—Pt 154 In—Pt 154 In—Pd 156 In—Pd 156In—Te 155 418 In—Te 156 418 Cu—Sn 186 227 Cu—Sn 186 227 Sn—Zn 199 Sn—Zn199 Au—Sn 217 252 Au—Sn 217 252 Ag—Sn 221 Ag—Sn 221 Al—Sn 228 Al—Sn 228Sn—Te 228 Sn—Te 228 Pd—Sn 230 Pd—Sn 230 Ge—Sn 231 Ge—Sn 231 Ni—Sn 231Ni—Sn 231 Sn—Ti 231 Sn—Ti 231 Cr—Sn 232 Cr—Sn 232 Nb—Sn 232 Nb—Sn 232Sn—Sn 232 Sn—Sn 232 Au—Cu 240 Au—Cu 240 Cu—Ni 250 350 Cu—Ni 250 350Ag—Te 295 353 Ag—Te 295 353 Cu—Te 340 Cu—Te 340 Al—Cr 350 Al—Cr 350Au—Ge 360 Au—Ge 360 Au—Si 363 Au—Si 363 Ge—Te 365 400 Ge—Te 365 400Cu—Pd 400 Cu—Pd 400 Cu—Pt 418 Cu—Pt 418

Although the foregoing refers to particular preferred embodiments, itwill be understood that the invention is not so limited. It will occurto those of ordinary skill in the art that various modifications may bemade to the disclosed embodiments and that such modifications areintended to be within the scope of the invention. Where an embodimentemploying a particular structure and/or configuration is illustrated inthe present disclosure, it is understood that the present invention maybe practiced with any other compatible structures and/or configurationsthat are functionally equivalent provided that such substitutions arenot explicitly forbidden or otherwise known to be impossible to one ofordinary skill in the art.

What is claimed is:
 1. A method of forming a device assembly,comprising: providing a backplane including a periodic array of multipleinstances of a backplane-side unit cell structure that comprises a setof backplane-side bonding structures including a common metal; providinga first source coupon including a first transfer substrate and aperiodic array of multiple instances of a first unit cell structure thatcomprises at least one first device and having a same periodicity as theperiodic array of multiple instances of the backplane-side unit cellstructure, wherein an instance of a first device-side bonding structureincluding a first metal is provided on one first device per each firstunit cell structure, and the common metal and the first metal areselected to provide a first bonding metallurgy having a first eutectictemperature upon bonding; transferring one first device from eachinstance of the first unit cell structure to the backplane by bondingrespective instances of the first device-side bonding structure tomatching backplane-side bonding structures, wherein a periodic array offirst bonded material portions having the first bonding metallurgy isformed while backplane-side bonding structures that are not bonded donot reflow; providing a second source coupon including a second transfersubstrate and a periodic array of multiple instances of a second unitcell structure that comprises at least one second device and having asame periodicity as the periodic array of multiple instances of thebackplane-side unit cell structure, wherein an instance of a seconddevice-side bonding structure including a second metal is provided onone second device per each second unit cell structure, and the commonmetal and the second metal are selected to provide a second bondingmetallurgy having a second eutectic temperature upon bonding, and thesecond eutectic temperature is greater than the first eutectictemperature; and transferring one second device from each instance ofthe second unit cell structure to the backplane by bonding respectiveinstances of the second device-side bonding structure to matchingbackplane-side bonding structures.
 2. The method of claim 1, wherein: aperiodic array of second bonded material portions having the secondbonding metallurgy is formed by transfer of the second devices; and theperiodic array of first bonded material portions changes composition bypartial evaporation of the first metal during transfer of the seconddevices.
 3. The method of claim 1, wherein: the first unit cellstructure comprises at least two first devices; an instance of the firstdevice-side bonding structure is provided on one of the at least twofirst devices; an instance of the second device-side bonding structureis provided on another of the at least two first devices; and firstdevices provided with respective instances of the second device-sidebonding structure are not transferred to the backplane during transferof the first devices provided with respective instances of the firstdevice-side bonding structure.
 4. The method of claim 3, whereininstances of the second device-side bonding structure on the firstdevices on the first transfer substrate are in physical contact withrespective backplane-side bonding structures without reflowing duringtransfer of the first devices provided with respective instances of thefirst device-side bonding structure to the backplane.
 5. The method ofclaim 3, wherein: the second unit cell structure comprises at least twosecond devices; an instance of the second device-side bonding structureis provided on one of the at least two second devices; an instance of athird device-side bonding structure comprising a third metal is providedon another of the at least two devices, wherein the common metal and thethird metal are selected to provide a third bonding metallurgy having athird eutectic temperature upon bonding, and the third eutectictemperature is greater than the first and second eutectic temperatures;and second devices provided with respective instances of the thirddevice-side bonding structure are not transferred to the backplaneduring transfer of the second devices provided with respective instancesof the second device-side bonding structure.
 6. The method of claim 5,wherein the first, second, and third devices comprise red light-emittingdiodes, green light-emitting diodes, and blue light-emitting diodes. 7.The method of claim 5, further comprising: providing a third sourcecoupon including a third transfer substrate and a periodic array ofmultiple instances of a third unit cell structure that comprises atleast one third device and having a same periodicity as the periodicarray of multiple instances of the backplane-side unit cell structure,wherein an instance of the third device-side bonding structure isprovided on one third device per each third unit cell structure; andtransferring one third device from each instance of the third unit cellstructure to the backplane by bonding respective instances of the thirddevice-side bonding structure to matching backplane-side bondingstructures.
 8. The method of claim 7, wherein: a periodic array of thirdbonded material portions having the third bonding metallurgy is formedby transfer of the third devices; the periodic array of first bondedmaterial portions changes composition by partial evaporation of thefirst metal during transfer of the third devices; and the periodic arrayof second bonded material portions changes composition by partialevaporation of the second metal during transfer of the third devices. 9.The method of claim 7, wherein each of the periodic array of firstbonded material portions, the periodic array of second bonded materialportions, and the periodic array of third bonded material portions has asame periodicity as the periodic array of multiple instances of thebackplane-side unit cell structure.
 10. The method of claim 9, whereinthe periodic array of multiple instances of the backplane-side unit cellstructure is a two-dimensional rectangular periodic array in which themultiple instances of the backplane-side unit cell structure arerepeated in two orthogonal directions that are perpendicular to asurface of the backplane.
 11. The method of claim 7, wherein the deviceassembly is an integrated light emitting device assembly that comprisesan emissive display panel containing light emitting diodes that emitthree or more different colors.
 12. The method of claim 11, wherein theemissive display panel comprises a direct view display panel containingred, green, and blue wavelength light emitting diodes and sensors bondedto the backplane.
 13. The method of claim 7, further comprising:providing a fourth source coupon including a fourth transfer substrateand a periodic array of multiple instances of a fourth unit cellstructure that comprises at least one fourth device and having a sameperiodicity as the periodic array of multiple instances of thebackplane-side unit cell structure, wherein an instance of the fourthdevice-side bonding structure is provided on one fourth device per eachfourth unit cell structure, and the common metal and the fourth metalare selected to provide a fourth bonding metallurgy having a fourtheutectic temperature upon bonding, and the fourth eutectic temperatureis greater than the first, second, and third eutectic temperatures; andtransferring one fourth device from each instance of the fourth unitcell structure to the backplane by bonding respective instances of thefourth device-side bonding structure to matching backplane-side bondingstructures, wherein a periodic array of fourth bonded material portionshaving the fourth bonding metallurgy is formed while the periodic arrayof first bonded material portions, the periodic array of second bondedmaterial portions, and the periodic array of fourth bonded materialportions do not reflow.